1. Field of the Invention
The present invention relates to a method of manufacturing a magnetic recording medium, and to a magnetic recording medium.
2. Description of the Related Art
In a magnetic recording medium it is important to make surface roughness extremely minimal in order to increase precision in recording and reading of data. For example, in the case of a hard disk, a floating-type head has become mainstream. In order to obtain good precision in recording and reading, the surface roughness must be extremely minimal and the head flying height must by kept within a small range.
Conventionally, in the manufacturing process for the hard disk or other magnetic recording medium, a front surface of a substrate is polished or otherwise made flat and then a recording layer and then a protective layer and the like are layered onto this substrate by means of a sputtering method. This kept the surface roughness of the overall magnetic recording medium extremely small (e.g., see Japanese Patent Laid-Open Publication Nos. H 5-314471, and H 9-231562).
However, even if the surface of the substrate is made flat, the surface roughness gradually increases in the course of layering the recording layer and the protective layer and the like on top of each other. Ultimately, the surface roughness of the magnetic recording medium overall exceeds a permissible range.
In recent years, in order to improve the surface recording density level, vertical recording type hard disks have increased. In this type of vertical recording hard disk, a soft magnetic layer which is thicker than the recording layer is provided between the substrate and the recording layer, causing the surface roughness of the magnetic recording medium overall to tend to increase.
Furthermore, as one possibility for a magnetic recording medium capable of achieving further increase in surface recording density, much attention is being given to a discreet type magnetic recording medium with a divided recording layer. However, in a discontinuous divided recording layer surface roughness is prone to increase.
By polishing the surface of the divided recording layer using a CMP (Chemical Mechanical polishing) method, it is possible to minimize the surface roughness of the discreet type magnetic recording medium. However, this approach has problems. In actuality, polishing of the thin divided recording layer is difficult to control, and chemical effects of the chemical liquids can cause degeneration of the divided recording layer and deterioration of its magnetic properties. Furthermore, using this type of polishing process reduces manufacturing efficiency.
Furthermore, as the surface recording density is improved the head flying height tends to be small. When the head flying height becomes small, the recording and reading in the magnetic recording medium become much less precise even if the surface roughness is of a size that would not have normally posed a problem conventionally.
The present invention has been made in light of the above-mentioned problems, and it is therefore an object of this invention to provide a method of manufacturing a magnetic recording medium capable of efficiently and reliably manufacturing a magnetic recording medium with little surface roughness and having good precision in recording and reading, and also to provide a magnetic recording medium with high surface recording density and good precision in reading and writing.